Conventionally, a technique for detecting AC and DC leakage and cutting off the supply of AC power to an electrical storage unit has been known (e.g., see Japanese Patent Application Publication No. JP2000-270463A).
Recently, as environmental awareness is raised and photovoltaic power generation is distributed, techniques for supplying a load, such as a battery of a hybrid vehicle, with DC power generated by a solar panel (a photovoltaic power generation apparatus) are studied. The configuration for supplying such DC power is provided in addition to the configuration for supplying AC power from a conventional commercial AC power supply, to selectively switch to a DC power or an AC power depending on a connected load.
It is described in Paragraph [0020] of Japanese Patent Application Publication No. JP2000-270463A that if a ground fault occurs in the vicinity of the electrical storage unit (or on the DC power source side) of an electric vehicle through a human body, DC leakage current flows along the path of a positive electrode of the electrical storage unit, the human body, the earth, a return cable of a switching unit of a leakage breaker, and a negative electrode of the electrical storage unit. In this case, a DC leakage detection unit detects the DC leakage current, and the leakage breaker cuts off the supply of power by opening the switching unit based on the output of the detection.
However, when the electrical storage unit (battery) of the electric vehicle is used as a load and the technique disclosed in the JP2000-270463A is applied to the configuration in which the electrical storage unit is recharged with DC power generated by a solar panel, there is a problem as follows. That is, when DC current leaks in the path reaching the load from the solar panel, i.e., a DC power supply, it is impossible to detect the leakage and cut off the supply of DC power from the solar panel.